U.S. patent number 6,216,459 [Application Number 09/459,243] was granted by the patent office on 2001-04-17 for exhaust gas re-circulation arrangement.
This patent grant is currently assigned to DaimlerChrysler AG. Invention is credited to Helmut Daudel, Helmut Finger, Erwin Schmidt, Siegfried Sumser.
United States Patent |
6,216,459 |
Daudel , et al. |
April 17, 2001 |
Exhaust gas re-circulation arrangement
Abstract
In an exhaust gas re-circulation arrangement for a supercharged
internal combustion engine including an exhaust gas turbocharger
with an exhaust gas turbine and a compressor, first and second
exhaust pipes extending from the engine separately to the exhaust
gas turbine, a charge air duct extending from the compressor to the
engine and an exhaust gas recirculation line extending from one of
the exhaust pipes upstream of the exhaust gas turbine to the charge
air duct downstream of the compressor, the exhaust gas turbine has
two turbine inlet flow passages, which provide for different flow
volumes and to each of which one of the exhaust pipes is connected
and a control arrangement is provided for controlling the exhaust
gas flow through the turbine inlet flow passages so as to control
the pressure in the exhaust gas re-circulation line to be higher
than in the charge air intake duct.
Inventors: |
Daudel; Helmut (Schorndorf,
DE), Finger; Helmut (Leinfelden-Echterdingen,
DE), Schmidt; Erwin (Baltmannsweiler, DE),
Sumser; Siegfried (Stuttgart, DE) |
Assignee: |
DaimlerChrysler AG (Stuttgart,
DE)
|
Family
ID: |
7890773 |
Appl.
No.: |
09/459,243 |
Filed: |
December 10, 1999 |
Foreign Application Priority Data
|
|
|
|
|
Dec 11, 1998 [DE] |
|
|
198 57 234 |
|
Current U.S.
Class: |
60/605.2;
60/602 |
Current CPC
Class: |
F02B
37/18 (20130101); F02D 9/06 (20130101); F02M
26/42 (20160201); F02M 26/34 (20160201); F02M
26/25 (20160201); F02M 26/05 (20160201); F02B
37/183 (20130101); F02C 6/12 (20130101); F02B
37/025 (20130101); F02C 3/34 (20130101); F02C
3/32 (20130101); F02M 26/38 (20160201); Y02T
10/144 (20130101); Y02T 10/12 (20130101); F02M
26/10 (20160201); F02B 37/007 (20130101) |
Current International
Class: |
F02C
3/00 (20060101); F02D 9/06 (20060101); F02C
3/32 (20060101); F02C 3/34 (20060101); F02M
25/07 (20060101); F02D 9/00 (20060101); F02C
6/00 (20060101); F02C 6/12 (20060101); F02M
025/07 () |
Field of
Search: |
;60/602,605.2
;415/158 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
28 55 687 |
|
Jun 1979 |
|
DE |
|
43 03 521 |
|
Jan 1994 |
|
DE |
|
43 30 487 |
|
Jan 1995 |
|
DE |
|
43 12 078 |
|
Jun 1995 |
|
DE |
|
44 29 232 |
|
Sep 1995 |
|
DE |
|
196 03 591 |
|
Mar 1997 |
|
DE |
|
Primary Examiner: Koczo; Michael
Attorney, Agent or Firm: Bach; Klaus J.
Claims
What is claimed is:
1. An exhaust gas re-circulation arrangement in a supercharged
internal combustion engine comprising: an exhaust gas turbocharger
with an exhaust gas turbine and a compressor, first and second
exhaust pipes extending from said engine separately to said exhaust
gas turbine, a charge air duct extending from said compressor to
said engine, an exhaust gas recirculation line extending from one
of said exhaust pipes upstream of said exhaust gas turbine to said
charge air duct downstream of said compressor, said exhaust gas
turbine having two inlet flow passages, one connected to said first
and the other to said second exhaust pipe and including means for
causing different exhaust gas flow volumes to pass through said
inlet flow passages, said turbine further having a variable
geometry for changing the relative flow volumes to pass through
said inlet flow passages, and a control arrangement for controlling
the exhaust gas flows to provide a pressure in said exhaust gas
re-circulation line, which is higher than the pressure of the
charge air in said charge air duct downstream of said
compressor.
2. An exhaust gas re-circulation arrangement according to claim 1,
wherein, in order to provide for different exhaust gas flow volumes
to pass through the two inlet flow passages, said inlet flow
passages are asymmetrical, one having a smaller flow cross-section
than the other.
3. An exhaust gas re-circulation arrangement according to claim 1,
wherein, in order to provide for different exhaust gas flow volumes
to pass through the two inlet flow passages, at least one of said
inlet flow passages includes at least one flow restriction.
4. An exhaust gas re-circulation arrangement according to claim 1,
wherein at least one of said inlet flow passages includes a
variable guide vane structure for achieving said variable geometry
of said exhaust gas turbine.
5. An exhaust gas re-circulation arrangement according to claim 3,
wherein said flow restriction comprises a variable guide vane
structure.
6. An exhaust gas re-circulation arrangement according to claim 1,
wherein a flow control device is connected to said exhaust pipe for
selectively supplying exhaust gas from the exhaust pipe leading to
one of said turbine inlet flow passages to the exhaust pipe leading
to the other inlet flow passage or to the turbine exhaust.
7. An exhaust gas re-circulation arrangement according to claim 1,
wherein said charge air duct includes a flow control device, which
is connected to the one exhaust pipe.
8. An exhaust gas re-circulation arrangement according to claim 7,
wherein said flow control device is a variable ejector.
9. An exhaust gas re-circulation arrangement according to claim 1,
wherein said adjustable guide vane structure comprises an axial
slide member.
10. An exhaust gas re-circulation arrangement according to claim 1,
wherein said exhaust gas turbocharger includes a supplemental
compressor for compressing exhaust gas for recirculation to said
charge air intake duct.
11. An exhaust gas re-circulation arrangement according to claim
10, wherein said exhaust gas turbocharger includes a shaft on which
all turbine, said compressor and said supplemental compressor are
disposed.
12. An exhaust gas re-circulation arrangement according to claim 1,
wherein said arrangement includes two of said turbochargers
arranged in parallel.
13. An exhaust gas re-circulation arrangement according to claim 1,
wherein said exhaust gas re-circulation line includes a flutter
valve.
Description
BACKGROUND OF THE INVENTION
The invention resides in an arrangement for the recirculation of
exhaust gases in an internal combustion engine.
In order to achieve the lowest possible emission limits,
particularly in connection with internal combustion engines for
commercial vehicles, exhaust gas re-circulation concepts are being
developed by which the NOx emissions are reduced without essential
increases in the fuel consumption. It is known for example, from DE
43 30 487 C1 and DE 43 03 521 C1 to provide a turbocharger, for
this purpose with an exhaust gas turbine which includes a variable
geometry such as an adjustable flow guide structure, rotatable
guide vanes, axially movable flow guide rings or similar devices.
By changing the geometry of the exhaust gas turbine, for example,
by closing the turbine flow guide structure, a turbine inlet
pressures p.sub.3 which is larger than the charge air pressure
P.sub.2 can be obtained over a large operating range up to full
engine power. As a result, the exhaust gas can be re-circulated
from a point of the exhaust pipe upstream of the turbine to the
charge air duct downstream of a charge air cooler (inter-cooler)
ahead of the engine without reducing the air/fuel ratio which would
affect the fuel consumption.
There are however problems since during full load operation the
cylinder pressure limit and also a compression pressure limit of
the exhaust gas turbocharger must be observed, whereby exhaust gas
re-circulation may be prevented or is at least limited. These
limits can be overcome in known arrangements only by additional
measures, which affect the overall efficiency of the gas exchange.
Additional measures are disclosed, for example, in DE 4 429 232 C1,
wherein variable ejectors serving as flow control apparatus, which
are arranged in the charge air duct, are disclosed. Also,
supplemental compressors for the compression of exhaust gas are
known for example from DE 43 12 078 C2.
Using adjustable guide vanes, it is possible to form, during engine
braking operation, a so-called turbo-brake wherein the turbine
guide vanes structure is adjusted to a very small flow
cross-section. As a result, the internal combustion engine is
highly charged whereby a very high engine braking power can be
obtained.
However, actual tests have shown that the long life expected from
engines, and in particular from commercial internal combustion
engines, cannot be achieved with the measures known so far.
DE OS 28 55 687 discloses an asymmetrical two-flow exhaust gas
turbine, wherein the two spiral inlet flow passages, which are
separated by a separating wall, are different in size. With the
asymmetrical separation, it is said that the pressure ahead of the
smaller inlet flow passage is higher than in the charge air duct so
that exhaust gas re-circulation is made possible. In order to
insure sufficient exhaust gas re-circulation also with high charge
air pressures a large difference in flow cross-section between the
two flow passages must be provided which detrimentally affects the
turbine efficiency, and generally the charge air exchange
efficiency of the engine.
It is the object of the present invention to provide an exhaust gas
re-circulation arrangement for a supercharged internal combustion
engine, which permits exhaust gas recirculation for the various
operating states of the engine without expensive supplemental
measures.
SUMMARY OF THE INVENTION
In an exhaust gas re-circulation arrangement for a supercharged
internal combustion engine including an exhaust gas turbocharger
with an exhaust gas turbine and a compressor, first and second
exhaust pipes extending from the engine separately to the exhaust
gas turbine, a charge air duct extending from the compressor to the
engine and an exhaust gas recirculation line extending from one of
the exhaust pipes upstream of the exhaust gas turbine to the charge
air duct downstream of the compressor, the exhaust gas turbine has
two turbine inlet flow passages, which provide for different flow
volumes and to each of which one of the exhaust pipes is connected
and a control arrangement is provided for controlling the exhaust
gas flow through the turbine inlet flow passages so as to control
the pressure in the exhaust gas re-circulation line to be higher
than in the charge air intake duct.
With the different inlet flow passages in combination with a
variable geometry of the exhaust gas turbine, for example, a
variable guide vane arrangement, the pressure of the recirculated
gas can be controlled by a control unit in such a way that, when
necessary, it is higher than the pressure of the charge air. As a
result, exhaust gas re-circulation can always be accomplished. At
the same time, it can be prevented by a particular control scheme,
that problems arise during full load operation.
In addition to being used as a turbo-brake, the variable geometry
may be formed for example by a vane ring structure, which is
slideable into one or both of the flow channels. It can be used to
control the pressure in the exhaust pipe recirculation line
upstream of the exhaust gas turbine and, consequently, also in the
exhaust gas re-circulation flow.
If, for example, an as high as possible variability with a
relatively high asymmetry of the flow channels is selected, the
exhaust pipe, in accordance with a particular embodiment of the
invention, may include a pressure release or gas redirecting
arrangement by way of which exhaust gas can flow from one to the
other of the turbine gas inlet passages or it can be blown off.
In this way, the turbo braking power can be limited and/or the
exhaust gas re-circulation volume and the exhaust gas pressure can
be controlled.
Since the turbine efficiency drops with increasing asymmetry also
the asymmetry may be limited and a pressure control device may be
provided in the charge air duct, for example in the form of a
variable ejector. It is also possible to provide a supplemental
compressor or a second exhaust gas turbocharger, which is arranged
in parallel with the first turbocharger.
Instead of, or in addition to, differently sized turbine inlet
passages, the inlet passages may have the same size, but a
restriction may be arranged in the exit area of one of the
passages. Such restriction may be provided for example by an
adjustable guide vane structure, which causes a desired pressure
build-up in one of the passages.
Below, two embodiments of the invention will be described in
greater detail on the basis of the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic representation of the invention using two
asymmetrical turbine inlet passages, and
FIG. 2 is an enlarged view of the exit area of one of the annular
turbine inlet passages including an adjustable guide vane structure
as a flow restriction.
DESCRIPTION OF PREFERRED EMBODIMENTS
As shown in the schematic representation of FIG. 1, fresh air is
compressed in a compressor 1 of an exhaust gas turbocharger 2.
After passing through a charge air cooler 3 and a flow control
device 4, which may be a variable ejector of a known design, the
compressed fresh air is supplied to an internal combustion engine 6
by way of a charge air duct 5. The internal combustion engine 6
includes two separate exhaust manifolds, one for each of two sets
of cylinders of the internal combustion engine (for example, the
left and the right side) From the exhaust manifolds the exhaust gas
is conducted through exhaust gas pipes 7A and 7B to an exhaust gas
turbine 8. The exhaust gas turbine 8 includes two spiral inlet flow
passages 9 and 10, which are separated from each other by an
intermediate wall 11. In the embodiment according to FIG. 1, the
annular inlet flow passage 9 is noticeably smaller than the annular
inlet flow passage 10. At the jointure of the two inlet passages,
there is provided, in a known manner, an adjustable guide vane
structure 12, which controls the exhaust gas flow to the turbine 8.
The turbine 8 is connected to the compressor 1 by a drive shaft 13.
Between the two exhaust gas pipes 7A and 7B, there is a flow
control arrangement 14 by way of which an exchange of gas flow
between the two exhaust pipes 9 and 10 can be established. Also,
the control arrangement 14 permits exhaust gas to be discharged to
an area downstream of the turbine 8 by way of a blow-off line 15.
In this way, a power and pressure limit for the motor-brake can be
provided, which is achieved by the variable geometry of the turbine
in accordance with the position of the guide vane structure 12. The
flow control arrangement 14 can also be used to influence the
exhaust gas volume, which is returned to the charge air intake duct
5 by way of the exhaust gas re-circulation line 16 as well as the
air/fuel ratio.
After being branched off the exhaust pipe 7A or 7B, the exhaust gas
is conducted first, by way of an exhaust gas recirculation valve
17, to an exhaust gas cooler 18 and then to a supplemental
compressor 19, before it is admitted to the charge air duct 5. If a
supplemental compressor 19 is used the flow control device 4 can be
omitted. The flow control device 4 is mainly provided for the case
in which, instead of being recirculated by way of a supplemental
compressor 19, the exhaust gas is re-circulated through the valve
20 directly by way of a branch off line 16b (shown in dashed lines)
to the exhaust gas re-circulation line 16.
In order to achieve exhaust gas re-circulation, it is only
necessary that the exhaust gas pressure P3l in the exhaust pipe 7A
or, respectively, the pressure P3r in the exhaust pipe 7B is higher
than the charge air pressure P2 ahead of the internal combustion
engine 6. If the exhaust gas is re-circulated by way of a
supplemental compressor, the pressures P3l and P3r may be lower
since the supplemental compressor provides subsequently for a
higher pressure as desired. A control unit 21 is provided, which
receives control values by way of a control line 22 according to a
desired engine performance graph. The control unit 21 supplies the
respective control signals for opening and closing the valve 17, or
respectively, 20 (selectively) to the flow control device 4 and the
positioner for the flow guide structure 12. In the flow control
device 4, that is, the ejector, the static pressure of the exhaust
gas is reduced when necessary.
The two valves 17 and 20, which are used alternatively may be
so-called flutter valves so that the pressure pulsations in the
exhaust gas system can be utilized for the exhaust gas
recirculation.
Instead of a supplemental compressor 19, a complete additional
exhaust gas turbocharger may be provided if necessary (not shown)
which is arranged in parallel with the exhaust gas turbocharger
2.
FIG. 2 is a sectional enlargement of a flow restriction by an
adjustable guide vane structure 12a for one of the two annular
turbine inlet flow passages, that is for the annular flow passage
9. Upon activation of the guide vane structure 12a, that is, when
the guide vane structure 12a is inserted into the flow passage 9,
the pressure in the annular flow passage is build up as
desired.
The arrangement as shown in FIG. 2 may be provided in addition to
differently sized annular inlet passages as shown in FIG. 1. Also,
the larger inlet flow passage 10 may be provided with a flow guide
vane structure 12, whereby a highly variable setup, which is
advantageous particularly for use as turbo brake arrangement is
obtained.
* * * * *